Various types of injection molds capable of numbering products being molded in high relief are known, one example being disclosed in GB-A-2 066 137 which relates to a mold for injection molding a plurality of plastic articles simultaneously with the articles being automatically numbered without repeating the combinations of algorithms, but without taking into consideration sequential numbering. The mold comprises two circular mold halves defining therebetween ten radially arranged cavities for producing the numbering, the individual numbers being embossed on a series of radially adjacent split rings of increasing diameter that are rotatable with respect to each other so that different combinations of numbers are produced along ten radii corresponding to the cavities. A frustoconical hub inside the innermost ring is forced outwardly of the respective mold half between injection cycles so as to loosen the split rings and thus allow relative rotation thereof by means of a counter mechanism. On closure of the mold halves, the frustoconical hub is forced into the plane of the respective mold half, this expanding the split rings to squeeze them against each other and thus avoid any gaps that would give rise to undesirable injection trimmings between the algorithms of the injection molded numbers.
As mentioned, the mold of GB-A-2 066 137 is designed to mold groups of ten numbers in each injection, counter mechanism being such as to ensure that sequential bering is avoided without any repetition of numbering being produced before all available number combinations have been used.
The prior art does not, however, include any numbering injection mold that is capable of injecting lots of twenty (rather than ten) products with serial numbering, the alteration of the numbering between each lot being automatic. The object of the present invention is therefore to provide an injection mold having such characteristics.